China on Friday denied accusations by Japan that a Chinese navy vessel had put a radar-lock on a Japanese warship near a group of disputed islands at the heart of a bitter feud between the two Asian nations.

The Chinese Ministry of National Defense said in a statement, its first official response to the claims, that Japanese officials had given out "false information" and "hyped up" the threat from China.

The Japanese allegations this week have put a fresh strain on relations between Tokyo and Beijing, which remain at loggerheads over who has sovereignty over the remote, rocky islands in the East China Sea.

The tensions have resulted in maritime standoffs and the scrambling of fighter jets in recent months. Japan currently administers the islands, but China has been regularly sending its own vessels on patrols in the surrounding waters.

Japanese Prime Minister Shinzo Abe on Wednesday described as "dangerous" and "regrettable" the actions of the Chinese frigate that Tokyo says used radar to gather information on the location of a Japanese destroyer in the East China Sea last week. That type of radar could be used to produce data needed to fire upon the Japanese vessel.

"Actions such as this escalate tensions and increase the risk of an incident or a miscalculation, and they could undermine peace, stability and economic growth in this vital region," Victoria Nuland, the spokeswoman for the State Department, said Tuesday.

The United States has tried to avoid getting dragged into the island dispute, saying it doesn't take sides on such competing claims of sovereignty. But U.S. officials have admitted that the islands fall under a mutual security treaty between Washington and Tokyo.

The Japanese call the disputed islands Senkaku, and China refers to them as Diaoyu. Near them are important shipping lanes, rich fishing grounds and possible mineral deposits.

Competing claims

Disagreement over who owns the small, uninhabited islands has soured diplomatic and economic relations between Japan and China since September, when Japan announced it had bought several of the islands from private Japanese owners.

China was outraged, as were protesters who marched through several Chinese cities calling for boycotts of Japanese products and asserting Beijing's sovereignty over the islands. Some of the protests turned violent, and damage to Japanese offices and businesses was reported.

In December, the dispute escalated when Japan scrambled fighter jets after a Chinese plane was seen near the islands. Chinese ships have repeatedly entered contested waters despite warnings from the Japanese Coast Guard.

China says its claim extends back hundreds of years. Japan says it saw no trace of Chinese control of the islands in an 1885 survey, so formally recognized them as Japanese sovereign territory in 1895. Japan then sold the islands in 1932 to descendants of the original settlers. The Japanese surrender at the end of World War II in 1945 only served to cloud the issue further.

The islands were administered by the U.S. occupation force after the war. But in 1972, Washington returned them to Japan as part of its withdrawal from Okinawa.

Tensions with Russia

Japan was given an abrupt reminder of a separate territorial dispute on Wednesday when its defense ministry said two Russian fighter jets entered Japanese airspace near the tip of the northern Japanese island of Hokkaido.

The Russian jets left Japanese airspace without incident after a little more than a minute, the ministry said.

The incident occurred near a set of islands disputed by Tokyo and Moscow since the end of World War II.

Asia's disputed islands

At first sight it looks like a scene from a post-apocalyptic movie. Journalist Tomas Etzler travels to one of the most remote locations in the South China Sea -- the front line of a dispute between the Philippines and China.